We considered the relative importance of several spatiotemporal scales of variability in sandy-shore macrobenthic community structure from a comprehensive inventory of the Gulf Islands National Seashore in 1993, including both Mississippi and Florida districts. Historical variation
also was considered through the comparison of macrobenthic data taken previously, in 1986–1987, from the same region. Macrobenthic community metrics, including species richness, diversity, total density, and community dissimilarity varied on several spatiotemporal scales, including landscape,
regional, historic, and seasonal levels. Community metrics all conveyed greater faunal complexity with decreasing exposure to wave disturbance, as effected by both seaward distance/depth and shore side. The nesting of macrobenthic variation did not directly parallel the hierarchy of spatiotemporal
scales. Rather, multivariate analyses showed hierarchically inclusive levels of community variation headed by the landscape scale, and successively followed by the regional scale, the historical scale, the habitat scale, and the seasonal scale. Macrobenthic assemblages were relatively similar
between historical and contemporary collections from the same district. Moderate seasonal variability in community metrics usually revealed greater faunal complexity in summer and autumn. Variability in total density across seasons, seaward distances, and sites was not driven by particular
dominant taxa; and dominant taxa occurred more consistently across seasons at individual locations than across stations within any given season. However, distinctive distribution patterns for the 23 selected common sandy-shore macrobenthic taxa used in multivariate analyses helped explain
the observed scales of variation. This study will have lasting value to the extent that it provides a multi-year regional comparative reference for future biodiversity assessments.
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